Various forms of saw-type cutting attachments heretofore have been provided for use in conjunction with power units including rotary output shafts. Examples of these previously known form of attachments are disclosed in U.S. Pat. Nos. 2,175,499, 2,621,685, 2,625,964, 2,668,567, 2,686,351, 2,816,583, 3,130,759, 3,398,588, 3,677,313, 3,807,242, 3,876,015 and 4,111,060.
However, these previously known forms of attachments are not capable of reciprocating a tool, in response to substantially constant rotary input torque, at substantially constant speed throughout major portions of the opposite directional strokes of the tool. Inasmuch as such constant speed movement greatly facilitates the cutting action of many types of reciprocal saw blades, a need therefore exists for a reciprocal saw attachment for rotary output shaft equipped power tools.